diff --git a/hooks/validate.sh b/hooks/validate.sh
index b429fa3..0a0cd88 100755
--- a/hooks/validate.sh
+++ b/hooks/validate.sh
@@ -17,22 +17,22 @@
 #
 #    You should have received a copy of the GNU Affero General Public License
 #    along with this program.  If not, see <https://www.gnu.org/licenses/>.
-#    
+#
 #    The interactive user interfaces in modified source and object code versions
 #    of this program must display Appropriate Legal Notices, as required under
 #    Section 5 of the GNU Affero General Public License version 3. In accordance
 #    with Section 7(b) of the GNU Affero General Public License, you must retain
 #    the Info line in every timestamp that is created or manipulated using a
 #    covered work.
-#    
+#
 #    You can be released from the requirements of the license by purchasing
 #    a commercial license. Buying such a license is mandatory as soon as you
 #    develop commercial activities involving this software without
 #    disclosing the source code of your own applications.
 #    These activities include: offering paid services to customers as an ASP,
-#    providing data storage and archival services, shipping this software with a 
+#    providing data storage and archival services, shipping this software with a
 #    closed source product.
-#    
+#
 #    For more information, please contact Mabulous GmbH at this
 #    address: info@mabulous.com
 #
@@ -44,6 +44,7 @@ if [[ ! -d "$DIR" ]]; then DIR="$PWD"; fi
 declare -i MINVERSION=$TIMESTAMPING_VERSION
 declare -i MAX_COMMITS_TO_CHECK=0
 declare -A PROCESSED_COMMIT
+declare -A PROCESSED_PARENT
 declare -A COMMITS
 declare -A COMMIT_TIMES
 
@@ -61,7 +62,7 @@ while [[ $# -gt 0 ]]; do
       if [ $MINVERSION -gt $TIMESTAMPING_VERSION ]; then
         echo_error "$KEY: this script only supports validating up to version $TIMESTAMPING_VERSION, but got $MINVERSION"
         exit 1
-      fi    
+      fi
       shift # past argument
       shift # past value
       ;;
@@ -323,12 +324,19 @@ validate_commit_and_parents() {
   local COMMIT_HASH="$1"
   log "validate_commit_and_parents for $COMMIT_HASH"
 
+  if [[ ${PROCESSED_PARENT[$COMMIT_HASH]} ]]; then
+    log "parents for $COMMIT_HASH have already been validated"
+    return 0;
+  else
+    PROCESSED_PARENT[$COMMIT_HASH]=1
+  fi
   local ALL_PASSED=true
   if ! validate_commit "$COMMIT_HASH"; then
     ALL_PASSED=false
   fi
   NUM_COMMITS_CHECKED=${#PROCESSED_COMMIT[@]}
   local PARENTS=$(git cat-file -p "$COMMIT_HASH" | awk '/^$/{exit} /parent/ {print}' | sed 's/parent //')
+
   #iterate over all parents of commit
   if [ ! -z "$PARENTS" ]; then
     while read PARENT_HASH; do
@@ -337,6 +345,7 @@ validate_commit_and_parents() {
       fi
     done <<< $(printf "%s" "$PARENTS")
   fi
+
   if [ "$ALL_PASSED" = true ]; then
     return 0
   fi